(1) Field of the Invention
The invention relates to automatic determination of speed of moving projectiles, and is directed more particularly to a system and method for determining the velocity of a projectile in an underwater launch tube.
(2) Description of the Prior Art
Devices for determining the velocity of projectiles in underwater launch tubes are generally well known. A system commonly in use in submarines for determining the velocity of a launched torpedo, as the torpedo travels through the torpedo tube, includes a wire fastened to the torpedo and wound upon a reel in the submarine outside of the torpedo tube. Travel of a launched torpedo through the tube causes the reel to rotate and activate a tachometer, the output of which is used to determine the velocity of the torpedo in the tube.
Such determination is used in producing an indication as to whether the torpedo was successfully "fired" and, if so, whether its departure speed is within prescribed parameters. In systems in which guidance is exercised on the torpedo after launch, the tube velocity data will be entered in a fire control system, wherein the speed of the torpedo is a critical factor.
In the above-described prior art system, it is necessary that the reel be rewound between firings, or launchings, which is time-consuming and given to errors and entanglements in pressure situations. In addition, there is substantial hardware associated with the reel and tachometer system. Still further, the wire from the torpedo to the wire reel passes through the torpedo tube breech door, a detriment to the "sub-safe" status of the submarine. It is a preferred design criterion in naval submarine marine architecture and in the design systems for the ejection of ordnance and other items from submerged submarines that there be no penetration of the pressure hull which would endanger the submarine within the submarine's range of operating depths. The expression "sub-safe" is a word of art in these fields that means a design has complied with this criterion.
Accordingly, it would be beneficial to have available a system having less in the way of hardware, a minimum of moving parts, and not requiring manual dexterity between firings, and requiring less time for resetting between firings. Further, it would be beneficial to have a system in which a sealed connector provides "sub-safe" conditions.